FIELD OF THE INVENTION
The invention relates to a method for producing UO.sub.2 or (U/Pu)O.sub.2 powder.
It is known for sinterable UO.sub.2 or (U/Pu)O.sub.2 to be compressed in powder form to make green compacts, and to produce sintered compacts from the green compacts. Such sintered compacts are introduced as nuclear fuel into the cladding tubes of fuel rods. The fuel rods are assembled to make nuclear reactor fuel assemblies. The nuclear reactor fuel assemblies are finally disposed in the reactor core of a nuclear reactor, which as a rule is moderated by light water.
It is also already conventional to obtain sinterable UO.sub.2 by heating ammonium uranyl carbonate. The ammonium uranyl carbonate is precipitated out of an aqueous solution of ammonium carbonate, into which gaseous uranium hexafluoride is introduced. Ammonium fluoride is produced as a further reaction product.
It is also already usual to convert uranium oxide, such as UO.sub.2, U.sub.3 O.sub.8, and UO.sub.3, into ammonium uranyl carbonate and from the ammonium uranyl carbonate to obtain sinterable UO.sub.2 powder by heating it. In that case as well, the ammonium uranyl carbonate is precipitated out in an aqueous ammonium carbonate solution. For that purpose, an aqueous uranyl nitrate solution is added to the aqueous ammonium carbonate solution, so that ammonium nitrate is produced as a byproduct. The aqueous uranyl nitrate solution in turn is obtained by dissolving the appropriate uranium oxide in nitric acid. That produces nitrous gases (NO.sub.x) as byproducts.
The nitrous gases are poisonous and can therefore not be vented to the atmosphere, but must instead be converted into harmless substances, such as nitrogen, water, or nitric acid.
The ammonium nitrate that occurs as a byproduct in the precipitation of the ammonium uranyl carbonate out of the aqueous ammonium carbonate solution is explosive and therefore requires proper safety precautions. Although it can be processed into synthetic fertilizer, and can also be thermally decomposed into nitrogen and water, the latter provision is especially difficult and expensive, and further processing into synthetic fertilizer requires complete decontamination of the ammonium nitrate solution, which once again involves considerable expense.